Antarctic sea ice in 2023

Every year, from June-October, polar local weather scientists from the Met Workplace produce a sequence of month-to-month sea ice briefings for the federal government and most of the people. These briefings describe the state of Arctic and Antarctic sea ice, examine how these relate to historic patterns, and, the place doable, assess causes of surprising behaviour.

Sea ice is frozen seawater that floats on the floor of the ocean and is discovered when temperatures are chilly sufficient for sea water to freeze. The extent of sea ice is a key local weather indicator, as a result of sea ice cowl insulates the ocean in winter and displays daylight in summer time, in addition to offering a habitat for a variety of species. 

Right here, Senior Scientist Alex West talks concerning the 2023 Antarctic sea ice minimal and its interplay with the ocean and environment.

Lowest sea ice extent on file

Antarctic common sea ice extent for 2023 was the bottom on file. Through the ice development season from June-October, ice extent was exceptionally low for the time of yr, reaching over 1 million sq. km beneath earlier file lows and setting a brand new file low most extent by a really giant margin. For a lot of the remainder of the yr, the ice was at file or near-record low ranges, recording a second successive file low minimal in February (Determine 1).

Determine 1. Antarctic sea ice extent in 2023 (daring black line) with different latest years indicated, in addition to earlier years with notably low sea ice extent. The 1981-2010 common can be proven, with the shaded area indicating 2 normal deviation intervals.

The very low extent from June-October was partly brought on by enhanced heat northerly winds, related to persistent areas of excessive and low strain (Ionita, 2024). Early within the ice development season, from Might-July, these have been concentrated close to the Antarctic Peninsula, within the Weddell and Bellingshausen Sea areas; later within the development season, from August-October, the strongest winds have been to be discovered additional west, within the Ross Sea. The place of the bottom sea ice situations modified equally.

Nonetheless, it’s probably that the ocean additionally performed an element. The low extent of 2023 continues a sample of very excessive variability in Antarctic sea ice since 2007, with first excessive after which low sea ice situations persisting for lengthy durations of time, in a method unlikely to be brought on by identified atmospheric modifications (Hobbs et al., 2024). A key second on this interval of excessive variability was a big discount that occurred in 2016, and that is considered linked to modifications within the higher ocean brought on by stronger westerly winds mixing hotter waters beneath in direction of the floor (Earys et al., 2021; Zhang et al., 2022). Additional mixing of heat waters can’t be dominated out as a further reason for the very low extent of 2023.

The exact contribution of anthropogenic (human-caused) international warming to the file low sea ice of 2023 just isn’t but identified. Whereas local weather fashions predict that Antarctic sea ice extent will lower in response to anthropogenic warming, variability up to now 15 years has been appreciable, with very excessive extent from 2012-2014 adopted by the present interval of very low extent (Determine 2). Additional excessive variability in both route stays doable within the years forward.

Determine 2. Antarctic sea ice month-to-month anomalies over the interval of satellite tv for pc observations. For every month, the 1981-2010 common ice extent for that month is subtracted. This largely removes the seasonal cycle in order that subtler long-term modifications could be seen extra simply.

Throughout April we’re exploring the subject of the ocean and local weather. Observe the #GetClimateReady hashtag on X (previously Twitter) to study extra all through the month.

References

Eayrs, C., X. Li, M.N. Raphael and D.M. Holland (2021) Speedy decline in Antarctic sea ice in recent times hints at future change. Nat. Geosci., 14, 460–464. https://doi.org/10.1038/s41561-021-00768-3

Hobbs, W., and Coauthors (2024): Observational Proof for a Regime Shift in Summer time Antarctic Sea Ice. J. Local weather, 37, 2263–2275, https://doi.org/10.1175/JCLI-D-23-0479.1

Ionita M (2024) Massive-scale drivers of the exceptionally low winter Antarctic sea ice extent in 2023. Entrance. Earth Sci. 12:1333706, https://doi.org/10.3389/feart.2024.1333706

Zhang, L., T.L. Delworth, X. Yang, F. Zeng, F. Lu, Y. Morioka and M. Bushuk (2022) The relative position of the subsurface Southern Ocean in driving unfavorable Antarctic Sea ice extent anomalies in 2016–2021. Commun. Earth Environ., 3, 302. https://doi.org/10.1038/s43247-022-00624-1

A map of Antarctica displaying the Antarctic Peninsula separated by the Bellingshausen and Weddell Seas. Map: Adobe Inventory.